Conventionally, a photographically useful reagent that is hardly soluble in water {e.g. an oil-soluble coupler; an antioxidant used in preventing fading, color fog, or color mixing (e.g. alkylhydroquinones, alkylphenols, chromans, and cumarones); a hardener, an oil-soluble filter dye, an oil-soluble ultraviolet absorber, an oil-soluble fluorescent whitening agent, a DIR compound (e.g. DIR hydroquinones and non-dye-forming DIR couplers), a developer, a dye developer, a DRR compound, and a DDR coupler} is used in the following manner. That is, the reagent is dissolved in a suitable oil agent, i.e. a high-boiling solvent; and the solution is dispersed in a hydrophilic organic colloid, especially an aqueous solution of gelatin, in the presence of a surface-active agent, to form a hydrophilic organic colloid layer (e.g. a light-sensitive emulsion layer, a filter layer, a backing layer, an antihalation layer, an intermediate layer, and a protective layer) having the reagent contained therein in a dispersed state. As the high-boiling organic solvent, a phthalate compound or a phosphate compound is generally used.
A phthalate compound and a phosphate compound that are high-boiling organic solvents are used in many cases because they are excellent, for example, in view of affinity to colloids, such as gelatin; dispersibility of couplers; influence on the stability of color-formed images; influence on the hue of color-formed images; chemical stability in light-sensitive materials; and inexpensive availability. However, these known high-boiling organic solvents (e.g. phthalate compounds and phosphate compounds) are unsatisfactory in view of, especially, the effect of preventing the occurrence of stain and fading of color images due to light, heat, and humidity, in the case of recent light-sensitive materials in which high performance is demanded. Thus, various requirements are placed on high-boiling organic solvents used in recent light-sensitive materials. General requirements are that, for example, they can be obtained or produced inexpensively; they are excellent in capability of dissolving photographically useful reagents or of dispersing photographically useful reagents stably; they do not have adverse effects on developability and photographic characteristics; they are excellent in chemical stability, and they are excellent in the effect of preventing fading of color images.
On the other hand, in color light-sensitive materials, the molecules of the dyes formed from pyrazoloazole magenta couplers or pyrroloazole cyan couplers that are excellent in hue, associate with each other readily in the film. The maximum absorption wavelength of the absorption by the association product is different from that of the single dye molecule itself. The larger the absorption by the association product is, the more unpreferable it is in view of the color reproduction. If the maximum absorption wavelength of a dye can be suitably made, without changing the structure of the dye itself, longer or shorter by adding an additive or the like to the same layer in which the dye is present, a color light-sensitive material whose color reproduction is more preferable can be provided inexpensively.
In connection with the above matter, it is found that among high-boiling organic solvents capable of becoming dispersion media for dye-forming nondiffusion couplers or the like, some high-boiling organic solvents have an effect of making shorter or longer the maximum absorption wavelength of yellow, magenta, or cyan dyes, or an effect of changing the absorption waveform by suppressing or promoting the association of the molecules of dyes. For example, urea compounds described in European Patent No. 0309160 A1, and amide compounds described in European Patent No. 0309160 A1, can be mentioned. However, in many cases these compounds are difficult to, simultaneously, make the hue of the dye preferable and make favorable the solubility and the dispersion stability of the required material, when the compounds are used as a dispersion medium. Also in many cases, the fading of the dyes formed by couplers, due to heat, humidity, or light is deteriorated. Compounds that can solve these problems are proposed and described in JP-A ("JP-A" means unexamined published Japanese patent application) Nos. 258800/1994, 258801/1994, and 258802/1994. However, the light-fading of the dyes formed by couplers obtained by using these compounds is not necessarily satisfactory, and further improvement is required.